Favicons in the vomnibar; remove support.

There are security issues with favicons as implemented previously.  This
commit removes favicon support entirely.
Merge pull request #1239 from smblott-github/favicons-revert

Favicons in the vomnibar; remove support.
Better default pattern in popup (https?://...).
Merge pull request #1240 from smblott-github/exclusion-rule-default-pattern

Better default exclusion-rule pattern in popup
Make contentEditable=true elements react properly to LinkHints
Fix contentEditable selection for elements with no children
Prevent exiting insert mode when a contentEditable element is active

We also detect when a contentEditable element is blurred by the mouse --
ie. another element is focused -- and make sure we *do* exit insert mode
accordingly.
Move checks for contentEditable to isInsertMode to reduce complexity
Add comments describing contentEditable methods in DOM utils
Add a comment to clarify the anchorNode/anchorElement difference
Merge branch 'fixContenteditable+DesignMode' of github.com:mrmr1993/vimium into smblott

Conflicts:
	background_scripts/completion.coffee
	content_scripts/vimium.css